The present invention relates to an image fixing method and developing agent, which can be applied to image formation by, for example, electrostatic recording apparatus and electrophotographic apparatus.
It is conventionally known, as discussed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-312169 that the fixation of a full-color image can be carried out at a low cost by combining a fixing roller having a surface layer made of a fluorine-containing resin such as ethylene tetrafluoride perfluoroether copolymer (PFA) and a wax-containing full-color toner.
Further, from the viewpoint of saving energy, the heat capacity of the fixing unit is reduced, and thus the time for warming up is shortened. This is also effective for reducing the cost. In order to reduce the heat capacity of the fixing unit, it is known to be effective that no rubber layer is used for the fixing roller, or the rubber layer is made thin.
It should be noted that when the rubber layer is thick, uniform fusion and uniform pressurization can be carried out, whereas when the layer is thin, there is a tendency that that the fusion and pressurization become uneven. While there is a demand of improving the quality of full-color images, if the fusion and pressurization are excessively carried out in a heat-pressure fixing step, dots are smashed. Thus, a touch of grittiness is caused on the image, making it impossible to obtain an excellent image. On the other hand, when the fusion and pressurization are uneven, irregular gloss is created in the solid image, thereby making the image quality uneven.
Additionally, in general, there is a strong demand of making a high gloss image in terms of a high-quality appearance of the color image and color reproducibility; however in some cases, matte-tone and glossless images are preferred for office use. To create a matte-tone image, the softening point of the toner can be high (about 145° C.), but it is very difficult to set conditions for fixing even such toner that has such a high softening point.
As described above, it is conventionally very difficult to optimize the thickness of the rubber layer of the fixing roller because the energy saving conditions, grittiness and evenness of the quality over the solid image conflict with each other.